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fsck.fat: Do not truncate files in cluster chain of size 2^32
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File with size 4294967295 (2^32-1) is stored in cluster chain of size
4294967296 (2^32). This cluster chain length cannot be represented in
32-bit integer so explicitly cast calculation to 64-bit (long long)
integer.

Before this change all files with size of 4294967295 bytes were auto
truncated to zero size because cluster chain size overflowed to zero.

This change fixes it and valid files are not automatically truncated.

Fixes: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1001845
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@pali
pali committed Feb 22, 2022
1 parent 1da41f0 commit ae94d63
Showing 1 changed file with 41 additions and 28 deletions.
69 changes: 41 additions & 28 deletions src/check.c
View file
Expand Up @@ -491,13 +491,17 @@ static int check_file(DOS_FS * fs, DOS_FILE * file)
break;
}
if (!(file->dir_ent.attr & ATTR_DIR) && le32toh(file->dir_ent.size) <=
clusters * fs->cluster_size) {
(unsigned long long)clusters * fs->cluster_size) {
printf
("%s\n File size is %u bytes, cluster chain length is > %u "
"bytes.\n Truncating file to %u bytes.\n", path_name(file),
("%s\n"
" File size is %u bytes, cluster chain length is %llu bytes.\n"
" Truncating file to %u bytes (%u clusters).\n",
path_name(file),
le32toh(file->dir_ent.size),
(unsigned)clusters * fs->cluster_size,
le32toh(file->dir_ent.size));
(unsigned long long)clusters * fs->cluster_size,
(((unsigned long long)clusters * fs->cluster_size <= UINT32_MAX) ?
(clusters * fs->cluster_size) : UINT32_MAX),
clusters);
truncate_file(fs, file, clusters);
break;
}
Expand All @@ -512,35 +516,35 @@ static int check_file(DOS_FS * fs, DOS_FILE * file)
break;
else {
if ((unsigned long long)clusters2 * fs->cluster_size >= UINT32_MAX)
die("Internal error: File size is larger than 2^32-1");
die("Internal error: Cluster chain is larger than 2^32");
clusters2++;
}
restart = file->dir_ent.attr & ATTR_DIR;
if (!owner->offset) {
printf(" Truncating second to %u bytes because first "
"is FAT32 root dir.\n",
(unsigned)clusters * fs->cluster_size);
printf(" Truncating second to %llu bytes (%u clusters) "
"because first is FAT32 root dir.\n",
(unsigned long long)clusters * fs->cluster_size, clusters);
do_trunc = 2;
} else if (!file->offset) {
printf(" Truncating first to %u bytes because second "
"is FAT32 root dir.\n",
(unsigned)clusters2 * fs->cluster_size);
printf(" Truncating first to %llu bytes (%u clusters) "
"because second is FAT32 root dir.\n",
(unsigned long long)clusters2 * fs->cluster_size, clusters);
do_trunc = 1;
} else {
char *trunc_first_string;
char *trunc_second_string;
char *noninteractive_string;

xasprintf(&trunc_first_string,
"Truncate first to %u bytes%s",
(unsigned)clusters2 * fs->cluster_size,
"Truncate first to %llu bytes (clusters %u)%s",
(unsigned long long)clusters2 * fs->cluster_size, clusters2,
restart ? " and restart" : "");
xasprintf(&trunc_second_string,
"Truncate second to %u bytes",
(unsigned)clusters * fs->cluster_size);
"Truncate second to %llu bytes (clusters %u)",
(unsigned long long)clusters * fs->cluster_size, clusters);
xasprintf(&noninteractive_string,
" Truncating second to %u bytes.",
(unsigned)clusters * fs->cluster_size);
" Truncating second to %llu bytes (clusters %u).",
(unsigned long long)clusters * fs->cluster_size, clusters);

do_trunc = get_choice(2, noninteractive_string,
2,
Expand All @@ -562,7 +566,10 @@ static int check_file(DOS_FS * fs, DOS_FILE * file)
set_fat(fs, prev, -1);
else
MODIFY_START(owner, 0, fs);
MODIFY(owner, size, htole32(clusters * fs->cluster_size));
if ((unsigned long long)clusters * fs->cluster_size > UINT32_MAX)
MODIFY(owner, size, htole32(UINT32_MAX));
else
MODIFY(owner, size, htole32(clusters * fs->cluster_size));
if (restart)
return 1;
while (this > 0 && this != -1) {
Expand All @@ -573,7 +580,7 @@ static int check_file(DOS_FS * fs, DOS_FILE * file)
break;
}
if ((unsigned long long)clusters * fs->cluster_size >= UINT32_MAX)
die("Internal error: File size is larger than 2^32-1");
die("Internal error: Cluster chain is larger than 2^32");
clusters++;
prev = this;
}
Expand All @@ -590,20 +597,26 @@ static int check_file(DOS_FS * fs, DOS_FILE * file)
}
set_owner(fs, curr, file);
if ((unsigned long long)clusters * fs->cluster_size >= UINT32_MAX)
die("Internal error: File size is larger than 2^32-1");
die("Internal error: Cluster chain is larger than 2^32");
clusters++;
prev = curr;
}
if (!(file->dir_ent.attr & ATTR_DIR) && le32toh(file->dir_ent.size) >
clusters * fs->cluster_size) {
(unsigned long long)clusters * fs->cluster_size) {
unsigned int new_size;
if ((unsigned long long)clusters * fs->cluster_size > UINT32_MAX)
new_size = UINT32_MAX;
else
new_size = clusters * fs->cluster_size;
printf
("%s\n File size is %u bytes, cluster chain length is %u bytes."
"\n Truncating file to %u bytes.\n", path_name(file),
("%s\n"
" File size is %u bytes, cluster chain length is %llu bytes.\n"
" Truncating file to %u bytes (%u clusters).\n",
path_name(file),
le32toh(file->dir_ent.size),
(unsigned)clusters * fs->cluster_size,
(unsigned)clusters * fs->cluster_size);
MODIFY(file, size,
htole32(clusters * fs->cluster_size));
(unsigned long long)clusters * fs->cluster_size,
new_size, clusters);
MODIFY(file, size, htole32(new_size));
}
return 0;
}
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