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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@mail.parknet.co.jp: cleanup and make sure to correct fake_offset]
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Tested-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Richard Weinberger <richard.weinberger@gmail.com>
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
OGAWA Hirofumi 2015-11-20 15:57:15 -08:00 committed by Linus Torvalds
parent 1817889e3b
commit 928a477102
1 changed files with 11 additions and 5 deletions
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16
fs/fat/dir.c
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@ -610,9 +610,9 @@ static int __fat_readdir(struct inode *inode, struct file *file,
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 @@ static int __fat_readdir(struct inode *inode, struct file *file,
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 @@ static int __fat_readdir(struct inode *inode, struct file *file,
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;
}