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authorVegard Nossum <vegard.nossum@gmail.com>2009-09-18 13:05:45 -0700
committeral <al@dizzy.pdmi.ras.ru>2009-09-24 08:40:15 -0400
commiteca6f534e61919b28fb21aafbd1c2983deae75be (patch)
treeb2c3f110a2defe6360004c39a074f3962ed0cc50 /fs/internal.h
parent6d729e44a55547c009d7a87ea66bff21a8e0afea (diff)
fs: fix overflow in sys_mount() for in-kernel calls
sys_mount() reads/copies a whole page for its "type" parameter. When do_mount_root() passes a kernel address that points to an object which is smaller than a whole page, copy_mount_options() will happily go past this memory object, possibly dereferencing "wild" pointers that could be in any state (hence the kmemcheck warning, which shows that parts of the next page are not even allocated). (The likelihood of something going wrong here is pretty low -- first of all this only applies to kernel calls to sys_mount(), which are mostly found in the boot code. Secondly, I guess if the page was not mapped, exact_copy_from_user() _would_ in fact handle it correctly because of its access_ok(), etc. checks.) But it is much nicer to avoid the dubious reads altogether, by stopping as soon as we find a NUL byte. Is there a good reason why we can't do something like this, using the already existing strndup_from_user()? [akpm@linux-foundation.org: make copy_mount_string() static] [AV: fix compat mount breakage, which involves undoing akpm's change above] Reported-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Pekka Enberg <penberg@cs.helsinki.fi> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: al <al@dizzy.pdmi.ras.ru>
Diffstat (limited to 'fs/internal.h')
-rw-r--r--fs/internal.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/internal.h b/fs/internal.h
index d55ef562f0b..515175b8b72 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -57,6 +57,7 @@ extern int check_unsafe_exec(struct linux_binprm *);
* namespace.c
*/
extern int copy_mount_options(const void __user *, unsigned long *);
+extern int copy_mount_string(const void __user *, char **);
extern void free_vfsmnt(struct vfsmount *);
extern struct vfsmount *alloc_vfsmnt(const char *);