Messages in this thread Patch in this message | | | From | Bernd Edlinger <> | Subject | [PATCHv2] Fix range checks in kernfs_get_target_path | Date | Sat, 7 Jul 2018 09:41:03 +0000 |
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The strncpy causes a warning [-Wstringop-truncation] here, which indicates that it never appends a NUL byte to the path. The NUL byte is only there because the buffer is allocated with kzalloc(PAGE_SIZE, GFP_KERNEL), but since the range-check is also off-by-one, and PAGE_SIZE==PATH_MAX the returned string will not be zero-terminated if it is exactly PATH_MAX characters. Furthermore also the initial loop may theoretically exceed PATH_MAX and cause a fault.
Signed-off-by: Bernd Edlinger <bernd.edlinger@hotmail.de> --- fs/kernfs/symlink.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/fs/kernfs/symlink.c b/fs/kernfs/symlink.c index 08ccabd..c8b7d44a 100644 --- a/fs/kernfs/symlink.c +++ b/fs/kernfs/symlink.c @@ -63,7 +63,10 @@ static int kernfs_get_target_path(struct kernfs_node if (base == kn) break;
- strcpy(s, "../"); + if ((s - path) + 3 >= PATH_MAX) + return -ENAMETOOLONG; + + memcpy(s, "../", 3); s += 3; base = base->parent; } @@ -79,16 +82,17 @@ static int kernfs_get_target_path(struct kernfs_node if (len < 2) return -EINVAL; len--; - if ((s - path) + len > PATH_MAX) + if ((s - path) + len >= PATH_MAX) return -ENAMETOOLONG;
/* reverse fillup of target string from target to base */ kn = target; + s[len] = '\0'; while (kn->parent && kn != base) { int slen = strlen(kn->name);
len -= slen; - strncpy(s + len, kn->name, slen); + memcpy(s + len, kn->name, slen); if (len) s[--len] = '/';
-- 1.9.1
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