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swapon: fix vfree() badness

PATCH In review Dave Chinner 3 participants 3 messages Sep 5, 2017 – Sep 13, 2017

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Memory management MM swap
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Dave Chinner

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#0 lore raw

PATCH 1/1 swapon: fix vfree() badness

From: Dave Chinner <[email protected]>

The cluster_info structure is allocated with kvzalloc(), which can return kmalloc'd or vmalloc'd memory. It must be paired with kvfree(), but sys_swapon uses vfree(), resultin in this warning from xfstests generic/357:

[ 1985.294915] swapon: swapfile has holes
[ 1985.296012] Trying to vfree() bad address (ffff88011569ac00)
[ 1985.297769] ------------[ cut here ]------------
[ 1985.299017] WARNING: CPU: 4 PID: 980 at mm/vmalloc.c:1521 __vunmap+0x97/0xb0
[ 1985.300868] CPU: 4 PID: 980 Comm: swapon Tainted: G        W       4.13.0-dgc #55
[ 1985.303086] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[ 1985.305421] task: ffff88083599c800 task.stack: ffffc90006d68000
[ 1985.306896] RIP: 0010:__vunmap+0x97/0xb0
[ 1985.307866] RSP: 0018:ffffc90006d6be68 EFLAGS: 00010296
[ 1985.309300] RAX: 0000000000000030 RBX: ffff88011569ac00 RCX: 0000000000000000
[ 1985.311066] RDX: ffff88013fc949d8 RSI: ffff88013fc8cb98 RDI: ffff88013fc8cb98
[ 1985.312803] RBP: ffffc90006d6be80 R08: 000000000004844c R09: 0000000000001578
[ 1985.314672] R10: ffffffff82271b20 R11: ffffffff8256e16d R12: 000000000000000a
[ 1985.316444] R13: 0000000000000001 R14: 00000000ffffffea R15: ffff880139a96000
[ 1985.318230] FS:  00007fb23ac0e880(0000) GS:ffff88013fc80000(0000) knlGS:0000000000000000
[ 1985.320081] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1985.321503] CR2: 0000564cdb0c7000 CR3: 0000000137448000 CR4: 00000000000406e0
[ 1985.323140] Call Trace:
[ 1985.323727]  vfree+0x2e/0x70
[ 1985.324403]  SyS_swapon+0x433/0x1080
[ 1985.325365]  entry_SYSCALL_64_fastpath+0x1a/0xa5

Fix this as well as the memory leak caused by a missing kvfree(frontswap_map) in the error handling code.

cc <[email protected]>
Signed-off-by Dave Chinner <[email protected]>
---
 mm/swapfile.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
mm/swapfile.c +2 -1
index 6ba4aab2db0b..a8952b6563c6 100644
@@ -3052,7 +3052,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	p->flags = 0;
 	spin_unlock(&swap_lock);
 	vfree(swap_map);
-	vfree(cluster_info);
+	kvfree(cluster_info);
+	kvfree(frontswap_map);
 	if (swap_file) {
 		if (inode && S_ISREG(inode->i_mode)) {
 			inode_unlock(inode);
Signature · 1 line
2.13.3
Reviewed-by on v1 1/1
#1 lore raw
Quoted 29 lines · Dave Chinner

From: Dave Chinner <[email protected]>

The cluster_info structure is allocated with kvzalloc(), which can return kmalloc'd or vmalloc'd memory. It must be paired with kvfree(), but sys_swapon uses vfree(), resultin in this warning from xfstests generic/357:

[ 1985.294915] swapon: swapfile has holes
[ 1985.296012] Trying to vfree() bad address (ffff88011569ac00)
[ 1985.297769] ------------[ cut here ]------------
[ 1985.299017] WARNING: CPU: 4 PID: 980 at mm/vmalloc.c:1521 __vunmap+0x97/0xb0
[ 1985.300868] CPU: 4 PID: 980 Comm: swapon Tainted: G        W       4.13.0-dgc #55
[ 1985.303086] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[ 1985.305421] task: ffff88083599c800 task.stack: ffffc90006d68000
[ 1985.306896] RIP: 0010:__vunmap+0x97/0xb0
[ 1985.307866] RSP: 0018:ffffc90006d6be68 EFLAGS: 00010296
[ 1985.309300] RAX: 0000000000000030 RBX: ffff88011569ac00 RCX: 0000000000000000
[ 1985.311066] RDX: ffff88013fc949d8 RSI: ffff88013fc8cb98 RDI: ffff88013fc8cb98
[ 1985.312803] RBP: ffffc90006d6be80 R08: 000000000004844c R09: 0000000000001578
[ 1985.314672] R10: ffffffff82271b20 R11: ffffffff8256e16d R12: 000000000000000a
[ 1985.316444] R13: 0000000000000001 R14: 00000000ffffffea R15: ffff880139a96000
[ 1985.318230] FS:  00007fb23ac0e880(0000) GS:ffff88013fc80000(0000) knlGS:0000000000000000
[ 1985.320081] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1985.321503] CR2: 0000564cdb0c7000 CR3: 0000000137448000 CR4: 00000000000406e0
[ 1985.323140] Call Trace:
[ 1985.323727]  vfree+0x2e/0x70
[ 1985.324403]  SyS_swapon+0x433/0x1080
[ 1985.325365]  entry_SYSCALL_64_fastpath+0x1a/0xa5
Quoted 5 lines

Fix this as well as the memory leak caused by a missing kvfree(frontswap_map) in the error handling code.

cc <[email protected]>
Signed-off-by Dave Chinner <[email protected]>
Reviewed-by Anshuman Khandual <[email protected]>
Quoted 9 lines
---
 mm/swapfile.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
mm/swapfile.c +0 -0
index 6ba4aab2db0b..a8952b6563c6 100644

mm/swapfile.c SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) · line 3056

Quoted 6 lines
mm/swapfile.c +2 -1
@@ -3052,7 +3052,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	p->flags = 0;
 	spin_unlock(&swap_lock);
 	vfree(swap_map);
-	vfree(cluster_info);
+	kvfree(cluster_info);
+	kvfree(frontswap_map);

Its correct in swapoff() system call but got missed here.

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#2 lore raw
In reply to Dave Chinner
Quoted 29 lines · Dave Chinner

From: Dave Chinner <[email protected]>

The cluster_info structure is allocated with kvzalloc(), which can return kmalloc'd or vmalloc'd memory. It must be paired with kvfree(), but sys_swapon uses vfree(), resultin in this warning from xfstests generic/357:

[ 1985.294915] swapon: swapfile has holes
[ 1985.296012] Trying to vfree() bad address (ffff88011569ac00)
[ 1985.297769] ------------[ cut here ]------------
[ 1985.299017] WARNING: CPU: 4 PID: 980 at mm/vmalloc.c:1521 __vunmap+0x97/0xb0
[ 1985.300868] CPU: 4 PID: 980 Comm: swapon Tainted: G        W       4.13.0-dgc #55
[ 1985.303086] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[ 1985.305421] task: ffff88083599c800 task.stack: ffffc90006d68000
[ 1985.306896] RIP: 0010:__vunmap+0x97/0xb0
[ 1985.307866] RSP: 0018:ffffc90006d6be68 EFLAGS: 00010296
[ 1985.309300] RAX: 0000000000000030 RBX: ffff88011569ac00 RCX: 0000000000000000
[ 1985.311066] RDX: ffff88013fc949d8 RSI: ffff88013fc8cb98 RDI: ffff88013fc8cb98
[ 1985.312803] RBP: ffffc90006d6be80 R08: 000000000004844c R09: 0000000000001578
[ 1985.314672] R10: ffffffff82271b20 R11: ffffffff8256e16d R12: 000000000000000a
[ 1985.316444] R13: 0000000000000001 R14: 00000000ffffffea R15: ffff880139a96000
[ 1985.318230] FS:  00007fb23ac0e880(0000) GS:ffff88013fc80000(0000) knlGS:0000000000000000
[ 1985.320081] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[ 1985.321503] CR2: 0000564cdb0c7000 CR3: 0000000137448000 CR4: 00000000000406e0
[ 1985.323140] Call Trace:
[ 1985.323727]  vfree+0x2e/0x70
[ 1985.324403]  SyS_swapon+0x433/0x1080
[ 1985.325365]  entry_SYSCALL_64_fastpath+0x1a/0xa5
Quoted 2 lines

Fix this as well as the memory leak caused by a missing kvfree(frontswap_map) in the error handling code.

Yes the patch is correct. Darrick has posted a similar fix
http://lkml.kernel.org/r/20170831233515.GR3775@magnolia and it is sitting in the Andrew's tree already (with the follow up from David to address frontswap_map)

Thanks!

Quoted 29 lines
cc <[email protected]>
Signed-off-by Dave Chinner <[email protected]>
---
 mm/swapfile.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
mm/swapfile.c +2 -1
index 6ba4aab2db0b..a8952b6563c6 100644
@@ -3052,7 +3052,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	p->flags = 0;
 	spin_unlock(&swap_lock);
 	vfree(swap_map);
-	vfree(cluster_info);
+	kvfree(cluster_info);
+	kvfree(frontswap_map);
 	if (swap_file) {
 		if (inode && S_ISREG(inode->i_mode)) {
 			inode_unlock(inode);
Signature · 7 lines
2.13.3

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Signature · 8 lines
Michal Hocko
SUSE Labs

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