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bootconfig: Fix negative seeks on 32-bit with LFS enabled

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Commit 26dda57695 "tools/bootconfig: Cleanup bootconfig footer size
calculations" replaced some expressions of type int with the
BOOTCONFIG_FOOTER_SIZE macro, which expands to an expression of type
size_t, which is unsigned.

On 32-bit architectures with LFS enabled (i.e. off_t is 64-bit), the
seek offset of -BOOTCONFIG_FOOTER_SIZE now turns into a positive
value.

Fix this by casting the size to off_t before negating it.

Just in case someone changes BOOTCONFIG_MAGIC_LEN to have type size_t
later, do the same thing to the seek offset of -BOOTCONFIG_MAGIC_LEN.

Link: https://lore.kernel.org/all/aKHlevxeg6Y7UQrz@decadent.org.uk/

Fixes: 26dda57695 ("tools/bootconfig: Cleanup bootconfig footer size calculations")
Signed-off-by: Ben Hutchings <benh@debian.org>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
This commit is contained in:
Ben Hutchings 2025-08-17 16:21:46 +02:00 committed by Masami Hiramatsu (Google)
parent c17b750b3a
commit 729dc340a4
1 changed files with 2 additions and 2 deletions
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4
tools/bootconfig/main.c
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@ -193,7 +193,7 @@ static int load_xbc_from_initrd(int fd, char **buf)
if (stat.st_size < BOOTCONFIG_FOOTER_SIZE)
return 0;
if (lseek(fd, -BOOTCONFIG_MAGIC_LEN, SEEK_END) < 0)
if (lseek(fd, -(off_t)BOOTCONFIG_MAGIC_LEN, SEEK_END) < 0)
return pr_errno("Failed to lseek for magic", -errno);
if (read(fd, magic, BOOTCONFIG_MAGIC_LEN) < 0)
@ -203,7 +203,7 @@ static int load_xbc_from_initrd(int fd, char **buf)
if (memcmp(magic, BOOTCONFIG_MAGIC, BOOTCONFIG_MAGIC_LEN) != 0)
return 0;
if (lseek(fd, -BOOTCONFIG_FOOTER_SIZE, SEEK_END) < 0)
if (lseek(fd, -(off_t)BOOTCONFIG_FOOTER_SIZE, SEEK_END) < 0)
return pr_errno("Failed to lseek for size", -errno);
if (read(fd, &size, sizeof(uint32_t)) < 0)