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ahci: fix cdrom read corruption

PATCH Superseded Jason Baron 4 participants 7 messages Jul 26, 2012 – Jul 27, 2012

v1 of 2 Superseded Latest is v2 →

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Jason Baron

author
#0 lore raw

cover ahci: fix cdrom read corruption

Hi,

While testing q35 I found data corruption on reads from the cdrom on the ahci controller. The first patch addresses this issue. I also notice that there is a memory leak in the ahci code, which is addressed in the second patch.

Thanks,

-Jason

Jason Baron (2):
ahci: Fix ahci cdrom read corruptions for reads > 128k
ahci: Fix sglist memleak in ahci_dma_rw_buf()

 hw/ide/ahci.c     |   44 +++++++++++++++++++++++++++++++++++++-------
 hw/ide/internal.h |    1 +
 2 files changed, 38 insertions(+), 7 deletions(-)
author
#1 lore raw

PATCH 1/2 ahci: Fix ahci cdrom read corruptions for reads > 128k

While testing q35, which has its cdrom attached to the ahci controller, I found that the Fedora 17 install would panic on boot. The panic occurs while squashfs is trying to read from the cdrom. The errors are:

[    8.622711] SQUASHFS error: xz_dec_run error, data probably corrupt
[    8.625180] SQUASHFS error: squashfs_read_data failed to read block

0x20be48a

I was also able to produce corrupt data reads using an installed piix based qemu machine, using 'dd'. I found that the corruptions were only occuring when the read size was greater than 128k. For example, the following command results in corrupted reads:

dd if=/dev/sr0 of=/tmp/blah bs=256k iflag=direct

The > 128k size reads exercise a different code path than 128k and below. In ide_atapi_cmd_read_dma_cb() s->io_buffer_size is capped at 128k. Thus, ide_atapi_cmd_read_dma_cb() is called a second time when the read is > 128k. However, ahci_dma_rw_buf() restart the read from offset 0, instead of at 128k. Thus, resulting in a corrupted read.

To fix this, I've introduced 'io_buffer_offset' field in IDEState to keep track of the offset. I've also modified ahci_populate_sglist() to take a new 3rd offset argument, so that the sglist is property initialized.

I've tested this patch using 'dd' testing, and Fedora 17 now correctly boots and installs on q35 with the cdrom ahci controller.

Signed-off-by Jason Baron <[email protected]>
---
 hw/ide/ahci.c     |   41 ++++++++++++++++++++++++++++++++++-------
 hw/ide/internal.h |    1 +
 2 files changed, 35 insertions(+), 7 deletions(-)
hw/ide/ahci.c +34 -7
index efea93f..9c95714 100644
@@ -636,7 +636,7 @@ static void ahci_write_fis_d2h(AHCIDevice *ad, uint8_t *cmd_fis)
     }
 }
 
-static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist)
+static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist, int offset)
 {
     AHCICmdHdr *cmd = ad->cur_cmd;
     uint32_t opts = le32_to_cpu(cmd->opts);

@@ -647,6 +647,10 @@ static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist)
     uint8_t *prdt;
     int i;
     int r = 0;
+    int sum = 0;
+    int off_idx = -1;
+    int off_pos = 0;
+    int tbl_entry_size;
 
     if (!sglist_alloc_hint) {
         DPRINTF(ad->port_no, "no sg list given by guest: 0x%08x\n", opts);

@@ -669,10 +673,31 @@ static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist)
     /* Get entries in the PRDT, init a qemu sglist accordingly */
     if (sglist_alloc_hint > 0) {
         AHCI_SG *tbl = (AHCI_SG *)prdt;
-
-        qemu_sglist_init(sglist, sglist_alloc_hint, ad->hba->dma);
+        sum = 0;
         for (i = 0; i < sglist_alloc_hint; i++) {
             /* flags_size is zero-based */
+            tbl_entry_size = (le32_to_cpu(tbl[i].flags_size) + 1);
+            if (offset <= (sum + tbl_entry_size)) {
+                off_idx = i;
+                off_pos = offset - sum;
+                break;
+            }
+            sum += tbl_entry_size;
+        }
+        if ((off_idx == -1) || (off_pos < 0) || (off_pos > tbl_entry_size)) {
+            fprintf(stderr, "%s: Incorrect offset! "
+                            "off_idx: %d, off_pos: %d\n",
+                            __func__, off_idx, off_pos);
+            r = -1;
+            goto out;
+        }
+
+        qemu_sglist_init(sglist, (sglist_alloc_hint - off_idx), ad->hba->dma);
+        qemu_sglist_add(sglist, le64_to_cpu(tbl[off_idx].addr + off_pos),
+                        le32_to_cpu(tbl[off_idx].flags_size) + 1 - off_pos);
+
+        for (i = off_idx + 1; i < sglist_alloc_hint; i++) {
+            /* flags_size is zero-based */
             qemu_sglist_add(sglist, le64_to_cpu(tbl[i].addr),
                             le32_to_cpu(tbl[i].flags_size) + 1);
         }

@@ -745,7 +770,7 @@ static void process_ncq_command(AHCIState *s, int port, uint8_t *cmd_fis,
             ncq_tfs->lba, ncq_tfs->lba + ncq_tfs->sector_count - 2,
             s->dev[port].port.ifs[0].nb_sectors - 1);
 
-    ahci_populate_sglist(&s->dev[port], &ncq_tfs->sglist);
+    ahci_populate_sglist(&s->dev[port], &ncq_tfs->sglist, 0);
     ncq_tfs->tag = tag;
 
     switch(ncq_fis->command) {

@@ -970,7 +995,7 @@ static int ahci_start_transfer(IDEDMA *dma)
         goto out;
     }
 
-    if (!ahci_populate_sglist(ad, &s->sg)) {
+    if (!ahci_populate_sglist(ad, &s->sg, 0)) {
         has_sglist = 1;
     }
 

@@ -1015,6 +1040,7 @@ static void ahci_start_dma(IDEDMA *dma, IDEState *s,
     DPRINTF(ad->port_no, "\n");
     ad->dma_cb = dma_cb;
     ad->dma_status |= BM_STATUS_DMAING;
+    s->io_buffer_offset = 0;
     dma_cb(s, 0);
 }
 

@@ -1023,7 +1049,7 @@ static int ahci_dma_prepare_buf(IDEDMA *dma, int is_write)
     AHCIDevice *ad = DO_UPCAST(AHCIDevice, dma, dma);
     IDEState *s = &ad->port.ifs[0];
 
-    ahci_populate_sglist(ad, &s->sg);
+    ahci_populate_sglist(ad, &s->sg, 0);
     s->io_buffer_size = s->sg.size;
 
     DPRINTF(ad->port_no, "len=%#x\n", s->io_buffer_size);

@@ -1037,7 +1063,7 @@ static int ahci_dma_rw_buf(IDEDMA *dma, int is_write)
     uint8_t *p = s->io_buffer + s->io_buffer_index;
     int l = s->io_buffer_size - s->io_buffer_index;
 
-    if (ahci_populate_sglist(ad, &s->sg)) {
+    if (ahci_populate_sglist(ad, &s->sg, s->io_buffer_offset)) {
         return 0;
     }
 

@@ -1050,6 +1076,7 @@ static int ahci_dma_rw_buf(IDEDMA *dma, int is_write)
     /* update number of transferred bytes */
     ad->cur_cmd->status = cpu_to_le32(le32_to_cpu(ad->cur_cmd->status) + l);
     s->io_buffer_index += l;
+    s->io_buffer_offset += l;
 
     DPRINTF(ad->port_no, "len=%#x\n", l);
hw/ide/internal.h +1 -0
index 7170bd9..bf7d313 100644
@@ -393,6 +393,7 @@ struct IDEState {
     struct iovec iov;
     QEMUIOVector qiov;
     /* ATA DMA state */
+    int io_buffer_offset;
     int io_buffer_size;
     QEMUSGList sg;
     /* PIO transfer handling */
Signature · 1 line
1.7.1
#2 lore raw

Re: [Qemu-devel] [PATCH 1/2] ahci: Fix ahci cdrom read corruptions for reads > 128k

Am 26.07.2012 21:40, schrieb Jason Baron:

Quoted 69 lines

While testing q35, which has its cdrom attached to the ahci controller, I found that the Fedora 17 install would panic on boot. The panic occurs while squashfs is trying to read from the cdrom. The errors are:

[    8.622711] SQUASHFS error: xz_dec_run error, data probably corrupt
[    8.625180] SQUASHFS error: squashfs_read_data failed to read block

0x20be48a

I was also able to produce corrupt data reads using an installed piix based qemu machine, using 'dd'. I found that the corruptions were only occuring when the read size was greater than 128k. For example, the following command results in corrupted reads:

dd if=/dev/sr0 of=/tmp/blah bs=256k iflag=direct

The > 128k size reads exercise a different code path than 128k and below. In ide_atapi_cmd_read_dma_cb() s->io_buffer_size is capped at 128k. Thus, ide_atapi_cmd_read_dma_cb() is called a second time when the read is > 128k. However, ahci_dma_rw_buf() restart the read from offset 0, instead of at 128k. Thus, resulting in a corrupted read.

To fix this, I've introduced 'io_buffer_offset' field in IDEState to keep track of the offset. I've also modified ahci_populate_sglist() to take a new 3rd offset argument, so that the sglist is property initialized.

I've tested this patch using 'dd' testing, and Fedora 17 now correctly boots and installs on q35 with the cdrom ahci controller.

Signed-off-by Jason Baron <[email protected]>
---
 hw/ide/ahci.c     |   41 ++++++++++++++++++++++++++++++++++-------
 hw/ide/internal.h |    1 +
 2 files changed, 35 insertions(+), 7 deletions(-)
hw/ide/ahci.c +8 -3
index efea93f..9c95714 100644
@@ -636,7 +636,7 @@ static void ahci_write_fis_d2h(AHCIDevice *ad, uint8_t *cmd_fis)
     }
 }
 
-static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist)
+static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist, int offset)
 {
     AHCICmdHdr *cmd = ad->cur_cmd;
     uint32_t opts = le32_to_cpu(cmd->opts);

@@ -647,6 +647,10 @@ static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist)
     uint8_t *prdt;
     int i;
     int r = 0;
+    int sum = 0;
+    int off_idx = -1;
+    int off_pos = 0;
+    int tbl_entry_size;
 
     if (!sglist_alloc_hint) {
         DPRINTF(ad->port_no, "no sg list given by guest: 0x%08x\n", opts);

@@ -669,10 +673,31 @@ static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist)
     /* Get entries in the PRDT, init a qemu sglist accordingly */
     if (sglist_alloc_hint > 0) {
         AHCI_SG *tbl = (AHCI_SG *)prdt;
-
-        qemu_sglist_init(sglist, sglist_alloc_hint, ad->hba->dma);
+        sum = 0;
         for (i = 0; i < sglist_alloc_hint; i++) {
             /* flags_size is zero-based */
+            tbl_entry_size = (le32_to_cpu(tbl[i].flags_size) + 1);
+            if (offset <= (sum + tbl_entry_size)) {

hw/ide/ahci.c static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist) · line 690

Quoted 10 lines
hw/ide/ahci.c +10 -0
+                off_idx = i;
+                off_pos = offset - sum;
+                break;
+            }
+            sum += tbl_entry_size;
+        }
+        if ((off_idx == -1) || (off_pos < 0) || (off_pos > tbl_entry_size)) {
+            fprintf(stderr, "%s: Incorrect offset! "
+                            "off_idx: %d, off_pos: %d\n",
+                            __func__, off_idx, off_pos);

I would use DPRINTF here, it's not a good idea to allow the guest to trigger fprintfs.

The rest looks good to me.

Kevin

author
#3 lore raw

Re: [Qemu-devel] [PATCH 1/2] ahci: Fix ahci cdrom read corruptions for reads > 128k

Quoted 75 lines · Kevin Wolf

Am 26.07.2012 21:40, schrieb Jason Baron:

Quoted 74 lines

While testing q35, which has its cdrom attached to the ahci controller, I found that the Fedora 17 install would panic on boot. The panic occurs while squashfs is trying to read from the cdrom. The errors are:

[    8.622711] SQUASHFS error: xz_dec_run error, data probably corrupt
[    8.625180] SQUASHFS error: squashfs_read_data failed to read block

0x20be48a

I was also able to produce corrupt data reads using an installed piix based qemu machine, using 'dd'. I found that the corruptions were only occuring when the read size was greater than 128k. For example, the following command results in corrupted reads:

dd if=/dev/sr0 of=/tmp/blah bs=256k iflag=direct

The > 128k size reads exercise a different code path than 128k and below. In ide_atapi_cmd_read_dma_cb() s->io_buffer_size is capped at 128k. Thus, ide_atapi_cmd_read_dma_cb() is called a second time when the read is > 128k. However, ahci_dma_rw_buf() restart the read from offset 0, instead of at 128k. Thus, resulting in a corrupted read.

To fix this, I've introduced 'io_buffer_offset' field in IDEState to keep track of the offset. I've also modified ahci_populate_sglist() to take a new 3rd offset argument, so that the sglist is property initialized.

I've tested this patch using 'dd' testing, and Fedora 17 now correctly boots and installs on q35 with the cdrom ahci controller.

Signed-off-by Jason Baron <[email protected]>
---
 hw/ide/ahci.c     |   41 ++++++++++++++++++++++++++++++++++-------
 hw/ide/internal.h |    1 +
 2 files changed, 35 insertions(+), 7 deletions(-)
hw/ide/ahci.c +13 -3
index efea93f..9c95714 100644
@@ -636,7 +636,7 @@ static void ahci_write_fis_d2h(AHCIDevice *ad, uint8_t *cmd_fis)
     }
 }
 
-static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist)
+static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist, int offset)
 {
     AHCICmdHdr *cmd = ad->cur_cmd;
     uint32_t opts = le32_to_cpu(cmd->opts);

@@ -647,6 +647,10 @@ static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist)
     uint8_t *prdt;
     int i;
     int r = 0;
+    int sum = 0;
+    int off_idx = -1;
+    int off_pos = 0;
+    int tbl_entry_size;
 
     if (!sglist_alloc_hint) {
         DPRINTF(ad->port_no, "no sg list given by guest: 0x%08x\n", opts);

@@ -669,10 +673,31 @@ static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist)
     /* Get entries in the PRDT, init a qemu sglist accordingly */
     if (sglist_alloc_hint > 0) {
         AHCI_SG *tbl = (AHCI_SG *)prdt;
-
-        qemu_sglist_init(sglist, sglist_alloc_hint, ad->hba->dma);
+        sum = 0;
         for (i = 0; i < sglist_alloc_hint; i++) {
             /* flags_size is zero-based */
+            tbl_entry_size = (le32_to_cpu(tbl[i].flags_size) + 1);
+            if (offset <= (sum + tbl_entry_size)) {
+                off_idx = i;
+                off_pos = offset - sum;
+                break;
+            }
+            sum += tbl_entry_size;
Quoted 9 lines

hw/ide/ahci.c static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist) · line 690

Quoted 5 lines
hw/ide/ahci.c +5 -0
+        }
+        if ((off_idx == -1) || (off_pos < 0) || (off_pos > tbl_entry_size)) {
+            fprintf(stderr, "%s: Incorrect offset! "
+                            "off_idx: %d, off_pos: %d\n",
+                            __func__, off_idx, off_pos);

I would use DPRINTF here, it's not a good idea to allow the guest to trigger fprintfs.

ok.

I'm also wondering if we need to 0 s->io_buffer_offset in more places than 'ahci_start_dma()'. For example, do we need it in ahci_dma_reset(), or ahci_dma_prepare_buf()? hw/ide/pci.c seems to do that.

I didn't include those places in my original patch, because I saw that start_dma was always called before rw_buf. But perhaps, there is another codepath that I missed.

Thanks,

-Jason

Tested-by on v1 1/2
#4 lore raw

Re: [Qemu-devel] [PATCH 1/2] ahci: Fix ahci cdrom read corruptions for reads > 128k

In reply to Jason Baron

Hi Jason,

Am 26.07.2012 21:40, schrieb Jason Baron:

Quoted 21 lines

While testing q35, which has its cdrom attached to the ahci controller, I found that the Fedora 17 install would panic on boot. The panic occurs while squashfs is trying to read from the cdrom. The errors are:

[    8.622711] SQUASHFS error: xz_dec_run error, data probably corrupt
[    8.625180] SQUASHFS error: squashfs_read_data failed to read block

0x20be48a

I was also able to produce corrupt data reads using an installed piix based qemu machine, using 'dd'. I found that the corruptions were only occuring when the read size was greater than 128k. For example, the following command results in corrupted reads:

dd if=/dev/sr0 of=/tmp/blah bs=256k iflag=direct

The > 128k size reads exercise a different code path than 128k and below. In ide_atapi_cmd_read_dma_cb() s->io_buffer_size is capped at 128k. Thus, ide_atapi_cmd_read_dma_cb() is called a second time when the read is > 128k. However, ahci_dma_rw_buf() restart the read from offset 0, instead of at 128k. Thus, resulting in a corrupted read.

Quoted 8 lines

To fix this, I've introduced 'io_buffer_offset' field in IDEState to keep track of the offset. I've also modified ahci_populate_sglist() to take a new 3rd offset argument, so that the sglist is property initialized.

I've tested this patch using 'dd' testing, and Fedora 17 now correctly boots and installs on q35 with the cdrom ahci controller.

Signed-off-by Jason Baron <[email protected]>
Tested-by Andreas Färber <[email protected]>

This also fixes my test case of running the "Check Installation Media" boot menu option on, e.g., openSUSE-12.1-GNOME-LiveCD-x86_64.iso with ich9-ahci (BNC#725008).

Thanks a lot for finding the root cause!

If you resubmit, please cc [email protected], I would very much like to backport this bugfix to stable-0.15 branch.

Regards,
Andreas

Signature · 2 lines
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
author
#5 lore raw

PATCH 2/2 ahci: Fix sglist memleak in ahci_dma_rw_buf()

In reply to Jason Baron

I noticed that in hw/ide/ahci:ahci_dma_rw_buf() does not appear to free the sglist. Thus, I've added a call to qemu_sglist_destroy() to fix this memory leak.

I'm wondering though if 'ahci_populate_sglist()' can return 0, and not populate the sglist, thus causing us to call free on NULL pointer. However, I see that ahci_start_transfer() always calls the free if the return is 0.

Signed-off-by Jason Baron <[email protected]>
---
 hw/ide/ahci.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
hw/ide/ahci.c +3 -0
index 9c95714..b48401d 100644
@@ -1073,6 +1073,9 @@ static int ahci_dma_rw_buf(IDEDMA *dma, int is_write)
         dma_buf_write(p, l, &s->sg);
     }
 
+    /* free sglist that was created in ahci_populate_sglist() */
+    qemu_sglist_destroy(&s->sg);
+
     /* update number of transferred bytes */
     ad->cur_cmd->status = cpu_to_le32(le32_to_cpu(ad->cur_cmd->status) + l);
     s->io_buffer_index += l;
Signature · 1 line
1.7.1
#6 lore raw

Re: [Qemu-devel] [PATCH 2/2] ahci: Fix sglist memleak in ahci_dma_rw_buf()

Il 26/07/2012 21:40, Jason Baron ha scritto:

Quoted 7 lines

I noticed that in hw/ide/ahci:ahci_dma_rw_buf() does not appear to free the sglist. Thus, I've added a call to qemu_sglist_destroy() to fix this memory leak.

I'm wondering though if 'ahci_populate_sglist()' can return 0, and not populate the sglist, thus causing us to call free on NULL pointer. However, I see that ahci_start_transfer() always calls the free if the return is 0.

A free(NULL) is ok, but a double-free would not be. Something like this would make me feel better:

dma-helpers.c +1 -0
index 35cb500..57725d0 100644
@@ -65,6 +65,7 @@
 void qemu_sglist_destroy(QEMUSGList *qsg)
 {
     g_free(qsg->sg);
+    memset(qsg, 0, sizeof(qsg));
 }
 
 typedef struct {

Paolo

Quoted 20 lines
Signed-off-by Jason Baron <[email protected]>
---
 hw/ide/ahci.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
hw/ide/ahci.c +3 -0
index 9c95714..b48401d 100644
@@ -1073,6 +1073,9 @@ static int ahci_dma_rw_buf(IDEDMA *dma, int is_write)
         dma_buf_write(p, l, &s->sg);
     }
 
+    /* free sglist that was created in ahci_populate_sglist() */
+    qemu_sglist_destroy(&s->sg);
+
     /* update number of transferred bytes */
     ad->cur_cmd->status = cpu_to_le32(le32_to_cpu(ad->cur_cmd->status) + l);
     s->io_buffer_index += l;