qnx4: Avoid confusing compiler about buffer lengths
cover qnx4: Avoid confusing compiler about buffer lengths
Hi,
This attempts to fix the issue Ronald Monthero found[1]. Avoids using a too-short struct buffer when reading the string, by using the existing struct union.
-Kees
[1] https://lore.kernel.org/lkml/[email protected]/
Kees Cook (2):
qnx4: Extract dir entry filename processing into helper
qnx4: Use get_directory_fname() in qnx4_match()
fs/qnx4/dir.c | 52 ++++++------------------------------------- fs/qnx4/namei.c | 29 +++++++++--------------- fs/qnx4/qnx4.h | 59 +++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 77 insertions(+), 63 deletions(-)
Signature · 1 line
2.34.1
PATCH 1/2 qnx4: Extract dir entry filename processing into helper
Both dir.c and namei.c need to perform the same work to figure out a directory entry's name and size. Extract this into a helper for use in the next patch.
Cc Anders Larsen <[email protected]>
Signed-off-by Kees Cook <[email protected]>
--- fs/qnx4/dir.c | 52 ++++++-------------------------------------- fs/qnx4/qnx4.h | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 66 insertions(+), 45 deletions(-)
fs/qnx4/dir.c +7 -45
@@ -15,43 +15,6 @@#include <linux/buffer_head.h> #include "qnx4.h" -/* -* A qnx4 directory entry is an inode entry or link info -* depending on the status field in the last byte. The -* first byte is where the name start either way, and a -* zero means it's empty. -* -* Also, due to a bug in gcc, we don't want to use the -* real (differently sized) name arrays in the inode and -* link entries, but always the 'de_name[]' one in the -* fake struct entry. -* -* See -* -* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6 -* -* for details, but basically gcc will take the size of the -* 'name' array from one of the used union entries randomly. -* -* This use of 'de_name[]' (48 bytes) avoids the false positive -* warnings that would happen if gcc decides to use 'inode.di_name' -* (16 bytes) even when the pointer and size were to come from -* 'link.dl_name' (48 bytes). -* -* In all cases the actual name pointer itself is the same, it's -* only the gcc internal 'what is the size of this field' logic -* that can get confused. -*/ -union qnx4_directory_entry { -struct { -const char de_name[48 ]; -u8 de_pad[15 ]; -u8 de_status; - }; -struct qnx4_inode_entry inode; -struct qnx4_link_info link; -}; -static int qnx4_readdir (struct file *file,struct dir_context *ctx) {struct inode *inode =file_inode (file);
@@ -74,26 +37,25 @@ static int qnx4_readdir(struct file *file, struct dir_context *ctx) ix = (ctx->pos >>QNX4_DIR_ENTRY_SIZE_BITS ) %QNX4_INODES_PER_BLOCK ;for (; ix <QNX4_INODES_PER_BLOCK ; ix++, ctx->pos +=QNX4_DIR_ENTRY_SIZE ) {union qnx4_directory_entry *de; +const char *fname; offset = ix *QNX4_DIR_ENTRY_SIZE ; de = (union qnx4_directory_entry *) (bh->b_data + offset); -if (!de->de_name[0 ]) -continue ; -if (!(de->de_status & (QNX4_FILE_USED |QNX4_FILE_LINK ))) + fname =get_entry_fname (de, &size); +if (!fname)continue ; +if (!(de->de_status &QNX4_FILE_LINK )) { - size =sizeof (de->inode.di_fname); ino = blknum *QNX4_INODES_PER_BLOCK + ix -1 ; }else { - size =sizeof (de->link.dl_fname); ino = (le32_to_cpu (de->link.dl_inode_blk) -1 ) *QNX4_INODES_PER_BLOCK + de->link.dl_inode_ndx; } - size =strnlen (de->de_name, size); -QNX4DEBUG ((KERN_INFO "qnx4_readdir:%.*s\n" , size, name)); -if (!dir_emit (ctx, de->de_name, size, ino,DT_UNKNOWN )) { + +QNX4DEBUG ((KERN_INFO "qnx4_readdir:%.*s\n" , size, fname)); +if (!dir_emit (ctx, fname, size, ino,DT_UNKNOWN )) {brelse (bh);return 0 ; }
fs/qnx4/qnx4.h +59 -0
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2.34.1
kernel test robot
build botRe: [PATCH 1/2] qnx4: Extract dir entry filename processing into helper
kernel test robot noticed the following build errors:
Hi Kees,
kernel test robot noticed the following build errors:
[auto build test ERROR on linus/master]
[also build test ERROR on v6.7-rc1 next-20231117]
[If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Kees-Cook/qnx4-Extract-dir-entry-filename-processing-into-helper/20231118-114223 base: linus/master patch link: https://lore.kernel.org/r/20231118033225.2181299-1-keescook%40chromium.org patch subject: [PATCH 1/2] qnx4: Extract dir entry filename processing into helper config: i386-randconfig-011-20231118 (https://download.01.org/0day-ci/archive/20231118/[email protected]/config) compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0 reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231118/[email protected]/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
All errors (new ones prefixed by >>):
In file included from fs/qnx4/dir.c:16:0:
>> fs/qnx4/qnx4.h:86:51: error: expected ',' before ')' token
offsetof(struct qnx4_link_info, dl_status));
^
fs/qnx4/qnx4.h:88:56: error: expected ',' before ')' token
offsetof(union qnx4_directory_entry, de_status));
^vim +86 fs/qnx4/qnx4.h
47
48 /*
49 * A qnx4 directory entry is an inode entry or link info
50 * depending on the status field in the last byte. The
51 * first byte is where the name start either way, and a
52 * zero means it's empty.
53 *
54 * Also, due to a bug in gcc, we don't want to use the
55 * real (differently sized) name arrays in the inode and
56 * link entries, but always the 'de_name[]' one in the
57 * fake struct entry.
58 *
59 * See
60 *
61 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6
62 *
63 * for details, but basically gcc will take the size of the
64 * 'name' array from one of the used union entries randomly.
65 *
66 * This use of 'de_name[]' (48 bytes) avoids the false positive
67 * warnings that would happen if gcc decides to use 'inode.di_name'
68 * (16 bytes) even when the pointer and size were to come from
69 * 'link.dl_name' (48 bytes).
70 *
71 * In all cases the actual name pointer itself is the same, it's
72 * only the gcc internal 'what is the size of this field' logic
73 * that can get confused.
74 */
75 union qnx4_directory_entry {
76 struct {
77 const char de_name[48];
78 u8 de_pad[15];
79 u8 de_status;
80 };
81 struct qnx4_inode_entry inode;
82 struct qnx4_link_info link;
83 };
84 /* Make sure the status byte is in the same place for all structs. */
85 _Static_assert(offsetof(struct qnx4_inode_entry, di_status) ==
> 86 offsetof(struct qnx4_link_info, dl_status));
87 _Static_assert(offsetof(struct qnx4_inode_entry, di_status) ==
88 offsetof(union qnx4_directory_entry, de_status));
89 Signature · 2 lines
0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
kernel test robot
build botRe: [PATCH 1/2] qnx4: Extract dir entry filename processing into helper
In reply to Kees Cookkernel test robot noticed the following build warnings:
Hi Kees,
kernel test robot noticed the following build warnings:
[auto build test WARNING on linus/master]
[also build test WARNING on v6.7-rc1 next-20231117]
[If your patch is applied to the wrong git tree, kindly drop us a note. And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Kees-Cook/qnx4-Extract-dir-entry-filename-processing-into-helper/20231118-114223 base: linus/master patch link: https://lore.kernel.org/r/20231118033225.2181299-1-keescook%40chromium.org patch subject: [PATCH 1/2] qnx4: Extract dir entry filename processing into helper config: hexagon-allmodconfig (https://download.01.org/0day-ci/archive/20231119/[email protected]/config) compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project.git 4a5ac14ee968ff0ad5d2cc1ffa0299048db4c88a) reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231119/[email protected]/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
All warnings (new ones prefixed by >>):
In file included from fs/qnx4/inode.c:20:
In file included from include/linux/pagemap.h:11:
In file included from include/linux/highmem.h:12:
In file included from include/linux/hardirq.h:11:
In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/hexagon/include/asm/io.h:337:
include/asm-generic/io.h:547:31: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
547 | val = __raw_readb(PCI_IOBASE + addr);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:560:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
560 | val = __le16_to_cpu((__le16 __force)__raw_readw(PCI_IOBASE + addr));
| ~~~~~~~~~~ ^
include/uapi/linux/byteorder/little_endian.h:37:51: note: expanded from macro '__le16_to_cpu'
37 | #define __le16_to_cpu(x) ((__force __u16)(__le16)(x))
| ^
In file included from fs/qnx4/inode.c:20:
In file included from include/linux/pagemap.h:11:
In file included from include/linux/highmem.h:12:
In file included from include/linux/hardirq.h:11:
In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/hexagon/include/asm/io.h:337:
include/asm-generic/io.h:573:61: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
573 | val = __le32_to_cpu((__le32 __force)__raw_readl(PCI_IOBASE + addr));
| ~~~~~~~~~~ ^
include/uapi/linux/byteorder/little_endian.h:35:51: note: expanded from macro '__le32_to_cpu'
35 | #define __le32_to_cpu(x) ((__force __u32)(__le32)(x))
| ^
In file included from fs/qnx4/inode.c:20:
In file included from include/linux/pagemap.h:11:
In file included from include/linux/highmem.h:12:
In file included from include/linux/hardirq.h:11:
In file included from ./arch/hexagon/include/generated/asm/hardirq.h:1:
In file included from include/asm-generic/hardirq.h:17:
In file included from include/linux/irq.h:20:
In file included from include/linux/io.h:13:
In file included from arch/hexagon/include/asm/io.h:337:
include/asm-generic/io.h:584:33: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
584 | __raw_writeb(value, PCI_IOBASE + addr);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:594:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
594 | __raw_writew((u16 __force)cpu_to_le16(value), PCI_IOBASE + addr);
| ~~~~~~~~~~ ^
include/asm-generic/io.h:604:59: warning: performing pointer arithmetic on a null pointer has undefined behavior [-Wnull-pointer-arithmetic]
604 | __raw_writel((u32 __force)cpu_to_le32(value), PCI_IOBASE + addr);
| ~~~~~~~~~~ ^
In file included from fs/qnx4/inode.c:24:
>> fs/qnx4/qnx4.h:86:51: warning: '_Static_assert' with no message is a C2x extension [-Wc2x-extensions]
86 | offsetof(struct qnx4_link_info, dl_status));
| ^
| , ""
fs/qnx4/qnx4.h:88:56: warning: '_Static_assert' with no message is a C2x extension [-Wc2x-extensions]
88 | offsetof(union qnx4_directory_entry, de_status));
| ^
| , ""8 warnings generated.
vim +/_Static_assert +86 fs/qnx4/qnx4.h
47
48 /*
49 * A qnx4 directory entry is an inode entry or link info
50 * depending on the status field in the last byte. The
51 * first byte is where the name start either way, and a
52 * zero means it's empty.
53 *
54 * Also, due to a bug in gcc, we don't want to use the
55 * real (differently sized) name arrays in the inode and
56 * link entries, but always the 'de_name[]' one in the
57 * fake struct entry.
58 *
59 * See
60 *
61 * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578#c6
62 *
63 * for details, but basically gcc will take the size of the
64 * 'name' array from one of the used union entries randomly.
65 *
66 * This use of 'de_name[]' (48 bytes) avoids the false positive
67 * warnings that would happen if gcc decides to use 'inode.di_name'
68 * (16 bytes) even when the pointer and size were to come from
69 * 'link.dl_name' (48 bytes).
70 *
71 * In all cases the actual name pointer itself is the same, it's
72 * only the gcc internal 'what is the size of this field' logic
73 * that can get confused.
74 */
75 union qnx4_directory_entry {
76 struct {
77 const char de_name[48];
78 u8 de_pad[15];
79 u8 de_status;
80 };
81 struct qnx4_inode_entry inode;
82 struct qnx4_link_info link;
83 };
84 /* Make sure the status byte is in the same place for all structs. */
85 _Static_assert(offsetof(struct qnx4_inode_entry, di_status) ==
> 86 offsetof(struct qnx4_link_info, dl_status));
87 _Static_assert(offsetof(struct qnx4_inode_entry, di_status) ==
88 offsetof(union qnx4_directory_entry, de_status));
89 Signature · 2 lines
0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
PATCH 2/2 qnx4: Use get_directory_fname() in qnx4_match()
In reply to Kees CookUse the new common directory entry name accessor helper to avoid confusing the compiler about over-running the file name buffer. Avoids false positive buffer overflow warning:
[ 4849.636861] detected buffer overflow in strlen [ 4849.636897] ------------[ cut here ]------------ [ 4849.636902] kernel BUG at lib/string.c:1165! ... [ 4849.637047] Call Trace: ... [ 4849.637251] qnx4_find_entry.cold+0xc/0x18 [qnx4] [ 4849.637264] qnx4_lookup+0x3c/0xa0 [qnx4]
Cc Anders Larsen <[email protected]>
Reported-by Ronald Monthero <[email protected]>
Signed-off-by Kees Cook <[email protected]>
--- fs/qnx4/namei.c | 29 +++++++++++------------------ 1 file changed, 11 insertions(+), 18 deletions(-)
fs/qnx4/namei.c +11 -18
@@ -26,31 +26,24 @@static int qnx4_match (int len,const char *name,struct buffer_head *bh,unsigned long *offset) { -struct qnx4_inode_entry *de; -int namelen, thislen; +union qnx4_directory_entry *de; +const char *fname; +int fnamelen;if (bh ==NULL ) {printk (KERN_WARNING "qnx4: matching unassigned buffer !\n" );return 0 ; } - de = (struct qnx4_inode_entry *) (bh->b_data + *offset); + de = (union qnx4_directory_entry *) (bh->b_data + *offset); *offset +=QNX4_DIR_ENTRY_SIZE ; -if ((de->di_status &QNX4_FILE_LINK ) !=0 ) { - namelen =QNX4_NAME_MAX ; - }else { - namelen =QNX4_SHORT_NAME_MAX ; - } - thislen =strlen ( de->di_fname ); -if ( thislen > namelen ) - thislen = namelen; -if (len != thislen) { + + fname =get_entry_fname (de, &fnamelen); +if (!fname || len != fnamelen)return 0 ; - } -if (strncmp (name, de->di_fname, len) ==0 ) { -if ((de->di_status & (QNX4_FILE_USED |QNX4_FILE_LINK )) !=0 ) { -return 1 ; - } - } + +if (strncmp (name, fname, len) ==0 ) +return 1 ; +return 0 ; }
Signature · 1 line
2.34.1