From: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
Subject: fat: fix fake_offset handling on error path
For the root directory, . and .. are faked (using dir_emit_dots()) and
ctx->pos is reset from 2 to 0.
A corrupted root directory could cause fat_get_entry() to fail, but
->iterate() (fat_readdir()) reports progress to the VFS (with ctx->pos
rewound to 0), so any following calls to ->iterate() continue to return
the same entries again and again.
The result is that userspace will never see the end of the directory,
causing e.g. 'ls' to hang in a getdents() loop.
[hirofumi@xxxxxxxxxxxxxxxxxx: cleanup and make sure to correct fake_offset]
Reported-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Tested-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Signed-off-by: Richard Weinberger <richard.weinberger@xxxxxxxxx>
Signed-off-by: OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/fat/dir.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
diff -puN fs/fat/dir.c~fat-fix-fake_offset-handling-on-error-path fs/fat/dir.c
--- a/fs/fat/dir.c~fat-fix-fake_offset-handling-on-error-path
+++ a/fs/fat/dir.c
@@ -610,9 +610,9 @@ parse_record:
int status = fat_parse_long(inode, &cpos, &bh, &de,
&unicode, &nr_slots);
if (status < 0) {
- ctx->pos = cpos;
+ bh = NULL;
ret = status;
- goto out;
+ goto end_of_dir;
} else if (status == PARSE_INVALID)
goto record_end;
else if (status == PARSE_NOT_LONGNAME)
@@ -654,8 +654,9 @@ parse_record:
fill_len = short_len;
start_filldir:
- if (!fake_offset)
- ctx->pos = cpos - (nr_slots + 1) * sizeof(struct msdos_dir_entry);
+ ctx->pos = cpos - (nr_slots + 1) * sizeof(struct msdos_dir_entry);
+ if (fake_offset && ctx->pos < 2)
+ ctx->pos = 2;
if (!memcmp(de->name, MSDOS_DOT, MSDOS_NAME)) {
if (!dir_emit_dot(file, ctx))
@@ -681,14 +682,19 @@ record_end:
fake_offset = 0;
ctx->pos = cpos;
goto get_new;
+
end_of_dir:
- ctx->pos = cpos;
+ if (fake_offset && cpos < 2)
+ ctx->pos = 2;
+ else
+ ctx->pos = cpos;
fill_failed:
brelse(bh);
if (unicode)
__putname(unicode);
out:
mutex_unlock(&sbi->s_lock);
+
return ret;
}
_
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