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um: Don't use vfprintf() for os_info()

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[ Upstream commit 236f9fe39b02c15fa5530b53e9cca48354394389 ]

The threads allocated inside the kernel have only a single page of
stack. Unfortunately, the vfprintf function in standard glibc may use
too much stack-space, overflowing it.

To make os_info safe to be used by helper threads, use the kernel
vscnprintf function into a smallish buffer and write out the information
to stderr.

Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Benjamin Berg 2023-11-10 12:03:41 +01:00 committed by Greg Kroah-Hartman
parent e4cc555388
commit ef21984653
1 changed files with 17 additions and 2 deletions
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19
arch/um/os-Linux/util.c
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@ -166,23 +166,38 @@ __uml_setup("quiet", quiet_cmd_param,
"quiet\n" "quiet\n"
" Turns off information messages during boot.\n\n"); " Turns off information messages during boot.\n\n");
/*
* The os_info/os_warn functions will be called by helper threads. These
* have a very limited stack size and using the libc formatting functions
* may overflow the stack.
* So pull in the kernel vscnprintf and use that instead with a fixed
* on-stack buffer.
*/
int vscnprintf(char *buf, size_t size, const char *fmt, va_list args);
void os_info(const char *fmt, ...) void os_info(const char *fmt, ...)
{ {
char buf[256];
va_list list; va_list list;
int len;
if (quiet_info) if (quiet_info)
return; return;
va_start(list, fmt); va_start(list, fmt);
vfprintf(stderr, fmt, list); len = vscnprintf(buf, sizeof(buf), fmt, list);
fwrite(buf, len, 1, stderr);
va_end(list); va_end(list);
} }
void os_warn(const char *fmt, ...) void os_warn(const char *fmt, ...)
{ {
char buf[256];
va_list list; va_list list;
int len;
va_start(list, fmt); va_start(list, fmt);
vfprintf(stderr, fmt, list); len = vscnprintf(buf, sizeof(buf), fmt, list);
fwrite(buf, len, 1, stderr);
va_end(list); va_end(list);
} }