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fat: fix buffer overflow in vfat_create_shortname()

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When using the string representation of a random counter as part of the base
name, ensure that it is no longer than 4 bytes.

Since we are repeatedly decrementing the counter in a loop until we have found a
unique base name, the counter may wrap around zero; therefore, it is not enough
to mask its higher bits before entering the loop, this must be done inside the
loop.

[hirofumi@mail.parknet.co.jp: use snprintf()]
Signed-off-by: Nikolaus Schulz <microschulz@web.de>
Cc: stable@kernel.org
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Nikolaus Schulz 2010-04-01 02:21:10 +09:00 committed by Linus Torvalds
parent 2eaa9cfdf3
commit 30d1872d9e
1 changed files with 3 additions and 3 deletions
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6
fs/fat/namei_vfat.c
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@ -309,7 +309,7 @@ static int vfat_create_shortname(struct inode *dir, struct nls_table *nls,
{
struct fat_mount_options *opts = &MSDOS_SB(dir->i_sb)->options;
wchar_t *ip, *ext_start, *end, *name_start;
unsigned char base[9], ext[4], buf[8], *p;
unsigned char base[9], ext[4], buf[5], *p;
unsigned char charbuf[NLS_MAX_CHARSET_SIZE];
int chl, chi;
int sz = 0, extlen, baselen, i, numtail_baselen, numtail2_baselen;
@ -467,7 +467,7 @@ static int vfat_create_shortname(struct inode *dir, struct nls_table *nls,
return 0;
}
i = jiffies & 0xffff;
i = jiffies;
sz = (jiffies >> 16) & 0x7;
if (baselen > 2) {
baselen = numtail2_baselen;
@ -476,7 +476,7 @@ static int vfat_create_shortname(struct inode *dir, struct nls_table *nls,
name_res[baselen + 4] = '~';
name_res[baselen + 5] = '1' + sz;
while (1) {
sprintf(buf, "%04X", i);
snprintf(buf, sizeof(buf), "%04X", i & 0xffff);
memcpy(&name_res[baselen], buf, 4);
if (vfat_find_form(dir, name_res) < 0)
break;