Commit 928a4771 authored Nov 20, 2015 by OGAWA Hirofumi Committed by Linus Torvalds Nov 20, 2015

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>

parent 1817889e

fs/fat/dir.c

+11 −5

Original line number	Diff line number	Diff line
		@@ -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);
		if (fake_offset && ctx->pos < 2)
		ctx->pos = 2;

		if (!memcmp(de->name, MSDOS_DOT, MSDOS_NAME)) {
		if (!dir_emit_dot(file, ctx))
		@@ -681,7 +682,11 @@ record_end:
		fake_offset = 0;
		ctx->pos = cpos;
		goto get_new;

		end_of_dir:
		if (fake_offset && cpos < 2)
		ctx->pos = 2;
		else
		ctx->pos = cpos;
		fill_failed:
		brelse(bh);
		@@ -689,6 +694,7 @@ fill_failed:
		__putname(unicode);
		out:
		mutex_unlock(&sbi->s_lock);

		return ret;
		}

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